On the effective electron mass in ultrathin films of IV-VI semiconductors in parallel magnetic field

In this paper, we study the effective electron mass at the Fermi level in ultrathin films of IV-VI semiconductors in a parallel magnetic field on the basis of a newly derived electron dispersion law. It is found, taking n-PbS, PbTe and PbSe as examples, that the effective Fermi-level mass depends on the subband index, in addition to the Fermi energy, due to the presence of the band non-parabolicity. The effective masses corresponding film thickness. The effective mass corresponding to the lowest subband is greater than the effective mass due to other subbands. Well known results for ultrathin films of relatively wide gap materials in the absence of magnetic field have been obtained as special cases of our generalized analysis. (authors)